This application claims the priority of German Application No. 10 2006 012 515.0, filed Mar. 18, 2006, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a motor vehicle and, more particularly, to a motor vehicle having a hybrid drive.
Motor vehicles which have at least two different drive units for generating the driving torque are generally known. A hybrid vehicle in the from of a BMW X5, having an internal-combustion engine and an electrical machine for generating driving torque, is described in the article “Tausendsassa” (“An Allround Winner”) of the trade journal Auto Motor und Sport, Edition 11/2004, Page 62, et. seq. Another hybrid vehicle with an internal-combustion engine and an electrical machine is known in the form of the Toyota Prius.
Hybrid vehicles can normally drive purely electrically over a certain driving distance or for a certain driving time. The time duration and speed or acceleration depend on the existing electrical power (in the form of the type of electrical machine used and its energy accumulator) and the charge condition of the energy accumulator supplying the electrical machine. When an energy accumulator is fully charged, a higher speed or a greater acceleration can be achieved by way of the electrical machine than in a partially empty charge condition. The operation of the internal-combustion engine has to be started before the energy accumulator is completely depleted, in order to continue to ensure a sufficient driving torque.
In the case of these known systems, as a rule, the driver is informed of the charge condition of the energy accumulator by way of a visual signal indication in the form of a colored luminous bar. However, this information is relatively inexact, so that the driver does not know exactly when to expect a corresponding loss of torque of the electrical machine and, therefore, when a transition to the internal-combustion operation or to a mixed operation takes place.
It is a disadvantage of such systems that, even in situations in which the driver would like to avoid an internal-combustion engine operation, for example, when maneuvering in an underground garage or in so-called stop-and-go traffic, he cannot reliably avoid it. Furthermore, situations are contemplated in which the driver, feeling the need to ensure safe driving, would like to start the operation of the internal-combustion engine purely as a precaution, for example, in the event that a considerable acceleration is immediately imminent, but in which situation this can also not be reliably ensured.
It is an object of the invention to eliminate the above-described disadvantages and provide a motor vehicle in which a considerably improved operability is ensured.
According to the invention, this object is achieved by a motor vehicle including two drive units for generating driving torque, the drive units being operable jointly as well as individually and separately for generating the driving torque, a device for defining a driver's intention, constructed as a twist grip throttle control acted upon by a restoring force or as an accelerator pedal acted upon by a restoring force, and a control unit for processing the driver's intention and for generating a control signal for controlling the drive units. The device for defining the driver's intention is constructed such that a force stage with an increased restoring force exists within the adjusting range of the device. The control unit is constructed such that, starting out from a driving operation in which only one driving device is active for generating a positive driving torque, when the force stage is exceeded, a switch-over from one driving device to the other, or a connection of the other driving device, takes place. Preferred further developments of the invention are also described and claimed herein.
According to the invention, a motor vehicle has at least two drive units for generating torque. One of the drive units is preferably constructed as an internal-combustion engine and the other drive unit is constructed as an electrical machine. The generating and providing of the driving torque in the transmission line can take place jointly by the two driving machines in that both machines generate driving torque and the latter is transmitted in a summed manner, for example, to a drive shaft—but it is also possible that (depending on the operating mode) drive torque is generated or provided either by one or the other of the drive units (thus either by the internal-combustion engine or by the electrical machine). Such arrangements are known, for example, as parallel hybrids. In a known manner, for example, by way of the deflection of an accelerator pedal, a driver's intention (driver's intention moment) is defined, and the latter is transmitted, for example, in the form of an electric signal, as an input signal to the control unit. The defined driver's intention is processed by the control unit and is transmitted in the form of one or more control variable(s) to the respective drive unit.
In the case of an internal-combustion engine, the control variables of the control unit control, for example, a throttle valve for controlling the air supply, an injection system for controlling the fuel feed, and/or an ignition system for controlling the ignition timing of the air-fuel mixture fed to the combustion chambers of the internal-combustion engine. In the case of an electrical driving machine, an electrical control variable for presetting a driving torque is transmitted to this electrical driving machine. According to the invention, the device for defining the driver's intention is constructed such that a force stage with an increased restoring force exists or can be generated. Furthermore, according to the invention, the control unit is constructed such that, starting from a driving operation in which only one of the driving devices for generating a positive torque is active, a switch-over from one driving device to the other, or a connection of the other driving device, takes place when the force stage is exceeded. The driver is thereby permitted to carry out a change-over between the drive units in a targeted manner.
The device for defining the driver's intention is preferably implemented by a so-called force feedback pedal. This type of accelerator pedal makes it possible to impress a force stage into the characteristic accelerator curve (which images the accelerator restoring force over the accelerator pedal travel or the accelerator pedal angle). The position of the force stage can be freely adjusted along the entire adjusting range of the accelerator pedal (entire accelerator pedal travel). The form (force intensity, travel range which the force stage is to cover, etc. . . . ) of the force stage may also be selected or adjusted arbitrarily. For a preferred case, in which the motor vehicle is constructed as a hybrid vehicle with an internal-combustion engine and an electrical driving machine, as a result of the force stage, the transition from the electrical machine to the internal-combustion engine operation or vice-versa can be intentionally initiated by the driver. Furthermore, starting from a deactivated operation (stopped motor) of the driving machines, for example, during a motor-stop-start operation, a starting of one or both drive units can be initiated.
In a preferred embodiment of the invention, beginning with a purely electrical driving operation, the force stage is used for connecting the internal-combustion engine when the force stage is exceeded, or switching-over to a pure internal-combustion engine operation. As an alternative or in addition, it is provided to, out of a stopped phase, during a motor stop-start operation of the motor vehicle, start the internal-combustion engine when the force stage is exceeded.
In a particularly preferred embodiment of the invention, the device for defining the driver's intention and/or the control unit coupled therewith are constructed such that the force stage can be arbitrarily positioned at different points within the adjusting range (for example, the accelerator pedal travel) of the device. This positioning preferably takes place as a function of the load condition of the energy accumulator supplying the electrical machine. As the energy accumulator discharged, the force stage is displaced in the direction of smaller accelerator pedal angles and vice-versa. This means that, when the energy accumulator is very full, the force stage is reached only at very large accelerator pedal angles (the accelerator pedal is very depressed) and, the more depleted the energy accumulator, the earlier (that is, at smaller accelerator pedal angles) the force stage is reached (as the energy accumulator becomes more depleted, the force stage is continuously more depressed in the direction of the accelerator rest position). As a result of the further development according to the invention, a driver is immediately capable of estimating whether or not it is worthwhile to continue to drive only electrically.
As an alternative or in addition, when the vehicle is stationary, especially during a motor stop-start operation, in case there is an automatic motor stop, the force stage is placed at the point at which the internal-combustion engine would start if the starting of the vehicle took place in the first gear position. This corresponds to a point with a very small accelerator pedal angle—this angle corresponding approximately to that angle which is defined in the case of the conventional automatic engine start for starting the internal-combustion engine. The accelerator pedal angle (total swiveling range) in the case of a conventional motor vehicle (passenger car) amounts to approximately 16 angular degrees. Here, only approximately 8 to 10 angular degrees of this total angle or entire swiveling range are utilized for the actual operation, while the remaining range no longer has an effect during an operation. On this basis, the automatic motor start should take place at approximately 10 to 20% of the overall operating path—in the case of a passenger car, therefore at the latest at a deflection of 2 angular degrees. Beginning from an automatic motor stop, when the force stage is reached, preferably the internal-combustion engine is started in order to reliably ensure a certain minimum driving torque.
The system is advantageously constructed such that, in the stationary position (for example, a motor stop) without an engaged gear position, the driver can start the operation of the internal-combustion engine when the clutch is operated (depressed) by bridging the force stage. As a result, a lead with respect to time is ensured, because otherwise the system first has to recognize the power demand from the electrical starting operation and has to start the operation of the internal-combustion engine during the acceleration operation. The obtained time lead represents a considerable gain with respect to safety. An unintentional starting of the operation of the internal-combustion engine is reliably prevented by the force stage.
Generally, in addition to the combination of the internal-combustion engine and the electrical machine, arbitrary other combinations of drive units are also contemplated, in which the idea according to the present invention may be implemented.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.